Light emitting display device

ABSTRACT

A light emitting display device includes: a light emitting element that includes a light emitting layer between a first electrode and a second electrode; a wavelength conversion layer overlapping the light emitting element; and an uneven layer that includes a plurality of furrows between the light emitting element and the wavelength conversion layer, wherein a shortest distance between a bottom surface of the plurality of furrows and the wavelength conversion layer is 0.1 um or greater.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 16/023,930 filed on Jun. 29, 2018, whichclaims the priority benefit of Korean Patent Application Nos.10-2017-0083798 and 10-2017-0126431 filed in Republic of Korea on Jun.30, 2017 and Sep. 28, 2017, respectively, all of which are herebyincorporated by reference in their entirety for all purposes as if fullyset forth herein.

BACKGROUND Field of the Disclosure

The present disclosure relates to a light emitting display device.

Description of the Background

A light emitting display device has a high response speed and a lowpower consumption and is self-luminescent differently from a liquidcrystal display device, and thus the light emitting display device hasan advantage in viewing angle and receives attraction as a nextgeneration display device.

The light emitting display device display images through an emission ofa light emitting element that includes a light emitting layer betweentwo electrodes.

However, since a part of a light emitted at the light emitting layer isnot output to the outside due to a total reflection at an interfacebetween the light emitting layer and the electrode or an interfacebetween a substrate and an air, a light extraction efficiency of thelight emitting display device can be reduced. Because of the low lightextraction efficiency, the light emitting display device has problemsthat brightness can be reduced and a power consumption can be increased.

SUMMARY

Accordingly, the present disclosure is directed to a light emittingdisplay device that substantially obviates one or more of the problemsdue to limitations and disadvantages of the related art.

In addition, the present disclosure is to provide a light emittingdisplay device that can improve an extraction efficiency of a lightemitted from a light emitting element.

Additional features and advantages of the disclosure will be set forthin the description which follows, and in part will be apparent from thedescription, or may be learned by practice of the disclosure. Theadvantages of the disclosure will be realized and attained by thestructure particularly pointed out in the written description and claimsas well as the appended drawings.

To achieve these and other advantages, and in accordance with thepurpose of the present disclosure, as embodied and broadly describedherein, a light emitting display device includes: a light emittingelement that includes a light emitting layer between a first electrodeand a second electrode; a wavelength conversion layer overlapping thelight emitting element; and an uneven layer that includes a plurality offurrows between the light emitting element and the wavelength conversionlayer, wherein a shortest distance between a bottom surface of theplurality of furrows and the wavelength conversion layer is 0.1 um orgreater.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate aspects of the disclosure andtogether with the description serve to explain the principles of thedisclosure.

In the drawings:

FIG. 1 is a circuit diagram illustrating a pixel region of a lightemitting display device according to a first aspect of the presentdisclosure;

FIG. 2 is a cross-sectional view illustrating a pixel region accordingto the first aspect of the present disclosure;

FIG. 3 is a view enlarging a portion A of FIG. 2;

FIG. 4 is a plan view illustrating a plan structure of an uneven layerof FIG. 2;

FIG. 5 is a view enlarging a portion A of FIG. 2;

FIG. 6 is a plan view illustrating an emission brightness at an unevenlayer of FIG. 2;

FIG. 7 is a cross-sectional view illustrating a pixel region accordingto the first aspect of the present disclosure;

FIG. 8 is a view illustrating a cross-sectional structure of an unevenlayer at a portion B of FIG. 7;

FIG. 9 is a view enlarging a portion B of FIG. 7;

FIG. 10 is a cross-sectional view illustrating a pixel region of a lightemitting display device according to a second aspect of the presentdisclosure;

FIG. 11 is a view enlarging a portion A of FIG. 10;

FIG. 12 is a graph illustrating a relation between an aspect ratio and acurrent efficiency enhancement for various aspect ratios of a wall; and

FIG. 13 is a graph illustrating a brightness efficiency according to arelation between an aspect ratio at half maximum and an aspect ratio athalf maximum over an aspect ratio of a wall.

DETAILED DESCRIPTION

Reference will now be made in detail to aspects, examples of which areillustrated in the accompanying drawings. The same or like referencenumbers may be used throughout the drawings to refer to the same or likeparts.

FIG. 1 is a circuit diagram illustrating a pixel region of a lightemitting display device according to a first aspect of the presentdisclosure.

Referring to FIG. 1, a pixel region of a light emitting display deviceof a first aspect includes a pixel circuit PC and a light emittingelement ED.

The pixel circuit PC is formed in a circuit region within the pixelregion that is defined by a gate line GL and a data line DL, and isconnected to the gate line GL, the data line DL and a first drivingpower source VDD. The pixel circuit PC responds to a gate on signal GSfrom the gate line GL to control an emission of the light emittingelement ED according to a data voltage Vdata from the data line DL. Thepixel circuit PC may include a switching thin film transistor (TFT) ST,a driving TFT DT, and a capacitor Cst.

The switching TFT ST includes a gate electrode connected to the gateline GL, a first source/drain electrode connected to the data line DL,and a second source/drain electrode connected to a gate electrode of thedriving TFT DT. The switching TFT ST supplies the data voltage Vdata tothe gate electrode of the driving TFT DT according to the gate on signalGS from the gate line GL.

The driving TFT includes the gate electrode connected to the secondsource/drain electrode of the switching TFT ST, a drain electrodeconnected to the first driving power source VDD, and a source electrodeconnected to the light emitting element ED. The driving TFT DT is turnedon according to a gate-source voltage based on the data voltage Vdata,which is supplied from the switching TFT ST, and controls a data signalidata supplied from the first driving power source VDD to the lightemitting element ED.

The capacitor Cst is connected between the gate electrode and the sourceelectrode of the driving TFT DT to store a voltage corresponding to thedata voltage Vdata supplied to the gate electrode of the driving TFT DT,and turns on the driving TFT DT with the stored voltage. The capacitorCst maintains the turn-on state of the driving TFT DT until a datavoltage Vdata is supplied through the switching TFT ST in a next frame.

The light emitting element ED is formed in a light emission regionwithin the pixel region and emits a light according to the data signalidata supplied from the pixel circuit PC.

The light emitting element ED may include a first electrode connected tothe source electrode of the driving TFT DT, a second electrode connectedto a second driving power source VSS, and a light emitting layer betweenthe first and second electrodes. The light emitting layer may includeone of an organic light emitting layer, an inorganic light emittinglayer and a quantum dot light emitting layer, or a stacked or mixedstructure of an organic light emitting layer (or an inorganic lightemitting layer) and a quantum dot light emitting layer.

The pixel region of this aspect controls the data signal idata, which issupplied to the light emitting element ED, according to the gate-sourcevoltage of the driving TFT DT depending on the data voltage Vdata, andemits the light emitting element ED to display images.

FIG. 2 is a cross-sectional view illustrating the pixel region accordingto the first aspect of the present disclosure.

Referring to FIG. 2, the pixel region of this aspect includes the pixelregion CA and the light emission region (or opening region) EA definedon a substrate 100.

The substrate 100 may be usually formed of a glass material, andalternatively, may be formed of a transparent plastic material having abendable or flexible property, for example, polyimide material. In casethat the plastic material is used for the substrate 100, consideringthat a deposition at high temperature is conducted, polyimide having anexcellent heat-resisting property may be used an entire surface of thesubstrate 100 may be covered by at least one buffer layer 110.

The buffer layer 110 serves to prevent a material contained in thesubstrate 100 diffusing to a transistor layer in a high-temperatureprocess among manufacturing processes of a TFT. Further, the bufferlayer 110 may serve to prevent an external moisture permeating to thelight emitting element ED. The buffer layer 110 may be made of siliconoxide or silicon nitride. Alternatively, the buffer layer 110 may beomitted.

The circuit region CA includes a transistor layer, a first insulatinglayer 130 and a second insulating layer 170.

The transistor layer includes the driving TFT DT.

The driving TFT DT may include an active layer 111, a gate insulatinglayer 113, a gate electrode 115, a passivation layer 117, a drainelectrode 119 d, and a source electrode 119 s.

The active layer 111 includes a channel region 111 c, a drain region 111d and a source region 111 s, which are formed at a TFT region of thecircuit region CA defined on the substrate 100 or the buffer layer 110.The active layer 111 includes the drain region 111 d and the sourceregion 111 s, which become conductive by an etching gas in an etchingprocess of the gate insulating layer 113, and the channel region 111 cwhich are not conductive. The drain region 111 d and the source region111 s may be spaced apart from each other with the channel region 111 ctherebetween.

The active layer 111 may be made of a semiconductor material including,but not limited to, at least one of amorphous silicon, polycrystallinesilicon, an oxide and an organic material. For example, the active layer111 may be formed of an oxide, such as zinc oxide, tin oxide, Ga—In—Znoxide, In—Zn oxide, or In—Sn oxide, or an oxide doped with an ion of Al,Ni, Cu, Ta, Mo, Zr, V, Hf or Ti.

The gate insulating layer 113 is formed on the channel region 111 c ofthe active layer 111. The gate insulating layer 113 may not be formedover an entire surface of the substrate 100 or buffer layer 110, may beformed in an island shape only on the channel region 111 c.

The gate electrode 115 is formed on the gate insulating layer 113 suchthat the gate electrode 115 overlaps the channel region 111 c. The gateelectrode 115 may serve as a mask such that the channel region 111 cdoes not become conductive by an etching gas in a process of patterningthe gate insulating layer 113 using an etching. The gate electrode 115may be made of Mo, Al, Cr, Au, Ti, Ni, Nd, Cu, or an alloy thereof, andmay be formed of a single-layered or multiple-layer structure using oneof the above metals or an alloy of the above metals.

The passivation layer 117 may be formed on the gate electrode 115, andthe drain region 111 d and the source region 111 s of the active layer111. In other words, the passivation layer 117 may be formed over anentire surface of the substrate 100 or the buffer layer 110 to cover thegate electrode 115 and the drain and source regions 111 d and 111 s ofthe active layer 111. The passivation layer 117 may be made of aninorganic material such as silicon oxide (SiOx) or silicon nitride(SiNx), or an organic material such as benzocyclobutene or photo acryl.The passivation layer 117 may be referred to as an inter-layeredinsulating layer.

The drain electrode 119 d is electrically connected to the drain region111 d through a first contact hole that is formed in the passivationlayer 117 overlapping the drain region 111 d.

The source electrode 119 s is electrically connected to the sourceregion 111 s through a second contact hole that is formed in thepassivation layer 117 overlapping the source region 111 s.

The drain and source electrodes 119 d and 119 s are made of the samemetal material, for example, Mo, Al, Cr, Au, Ti, Ni, Nd, Cu, or an alloythereof, and may be formed of a single-layered or multiple-layerstructure using one of the above metals or an alloy of the above metals.

Further, the circuit region CA includes a switching TFT and a capacitor.

The switching TFT is formed in the circuit region CA with the samestructure as the driving TFT DT, and detailed explanations of theswitching TFT are omitted.

The capacitor is formed at an overlapping region between the gateelectrode 115 and the source electrode 119 s of the driving TFT DT withthe passivation layer 117 therebetween.

A TFT in the circuit region CA may have a property of a thresholdvoltage being shifted by a light, and to prevent this, the lightemitting display device of this aspect may further include a lightshielding layer 101 located below the active layer 111.

The light shielding layer 101 is formed between the substrate 100 andthe active layer 111 and shields the active layer 111 from a lightincident toward the active layer 111 through the substrate 100, and thusa threshold voltage change of a TFT by an external light is prevented.The light shielding layer 101 may be covered by the buffer layer 110.Selectively, the light shielding layer 101 may be connected to a sourceelectrode of a TFT and serve as a bottom gate electrode of this TFT, andin this case, not only a property change by a light but also a thresholdvoltage change according to a bias voltage are minimized or prevented.

The first insulating layer 130 is formed on the substrate 100 to coverthe transistor layer. In other words, the first insulating layer 130covers the drain and source electrodes 119 d and 119 s and thepassivation layer 117. The first insulating layer 130 may be made of aninorganic material such as silicon oxide or silicon nitride. The firstinsulating layer 130 may be referred to as a passivation layer.

The second insulating layer 170 is formed on the substrate 100 to coverthe first insulating layer 130. The second insulating layer 170 isformed to have a relatively thick thickness and serves to provide a flatsurface. The second insulating layer 170 may be made of an organicmaterial such as photo acryl, benzocyclobutene, polyimide or fluorineresin.

The light emission region EA includes a wavelength conversion layer 150,an uneven layer 180, and a light emitting element ED.

The wavelength conversion layer 150 is formed on the first insulatinglayer 130 overlapping the light emission region EA. In other words, thewavelength conversion layer 150 is supported by the first insulatinglayer 130 and is covered by the second insulating layer 170 so that thewavelength conversion layer 150 is located between the first insulatinglayer 130 and the uneven layer 180 and overlaps the light emittingelement ED.

The wavelength conversion layer 150 may include a color filter thattransmits a wavelength of a color light, which is set (or defined) atits pixel region, out of a white light emitted from the light emittingelement ED toward the substrate 100. Alternatively, the wavelengthconversion layer 150 may transmits a wavelength of red, green or blue.For example, in the light emitting display device, one unit pixel mayconsist of neighboring first to third pixel regions, and in this case, awavelength conversion layer of the first pixel region may include a redcolor filter, a wavelength conversion layer of the second pixel regionmay include a green color filter, and a wavelength conversion layer ofthe third pixel region may include a blue color filter. Further, in thelight emitting display device, one unit pixel may include a white pixelregion that has no wavelength conversion layer.

Alternatively, the wavelength conversion layer 150 may include a quantumdot that has a size to re-emit according to a white light emitted fromthe light emitting element ED toward the substrate 100 and output alight of a color set at its pixel region. The quantum dot may beselected from CdS, CdSe, CdTe, ZnS, ZnSe, CdZnSeS, GaAs, GaP, GaAs—P,Ga—Sb, InAs, InP, InSb, AlAs, AlP or AlSb. For example, a wavelengthconversion layer of a first pixel region may include a quantum dot ofCdSe or InP, a wavelength conversion layer of a second pixel region mayinclude a quantum dot of CdZnSeS, a wavelength conversion layer of athird pixel region may include a quantum dot of ZnSe. The light emittingdisplay device using the wavelength conversion layer 150 with a quantumdot can have a high color reproduction range.

Alternatively, the wavelength conversion layer 150 may be formed of acolor filter containing a quantum dot.

The uneven layer 180 may be located at the second insulating layer 170to have an uneven shape, and changes a traveling path of a light emittedfrom the light emitting element ED, and thus increases a lightextraction efficiency of a pixel region. The uneven layer 180 includes aplurality of furrows 181 located between the light emitting element EDand the wavelength conversion layer 150. In other words, the unevenlayer 180 may include a plurality of furrows 181 and a wall 183.

Each of the plurality of furrow 181 is formed concavely from a frontsurface (or top surface) 170 a of the second insulating layer 170. Withrespect to the front surface 170 a of the second insulating layer 170,each of the plurality of furrows 181 may have the same depth, and due toa manufacturing process error in a patterning process for the unevenlayer 180, a part of the plurality of furrows 181 may have a differentdepth.

A bottom surface (or lowest surface) of each furrow 181 is separate at apredetermined distance from the wavelength conversion layer 150. Inorder that a front surface 150 a of the wavelength conversion layer 150being directly exposed to the furrows 181 due to the depth of thefurrows 181 is prevented, a shortest distance from the bottom surface ofthe furrows 181 to the wavelength conversion layer 150 may be 0.1 um orgreater. In this case, the second insulating layer 170 between thebottom surface of the furrows 181 and the wavelength conversion layer150 may have a thickness of 0.1 um or greater. In case that the secondinsulating layer 170 between the bottom surface of the furrows 181 andthe wavelength conversion layer 150 has a thickness less than 0.1 um, ina patterning process for the uneven layer 180, a part of the wavelengthconversion layer 150 may be directly exposed to the furrow 181, and thusa property of the light emitting element ED formed on the uneven layer180 may be deteriorated.

The wall 183 may have a structure to define or surround each furrow 181.The wall 183 changes a traveling path of a light from the light emittingelement ED toward substrate 100 and increases an extraction efficiencyof a light from the light emitting element ED.

The light emitting element ED may emit a light in a direction to thesubstrate 100 according to a bottom emission type. The light emittingelement ED may include a first electrode E1, a light emitting layer EL,and a second electrode E2.

The first electrode E1 is formed on the uneven layer 180 of the lightemission region EA and is electrically connected to the source electrode119 s of the driving TFT DT.

An end of the first electrode E1 adjacent to the circuit region CAextends over the source electrode 119 s of the driving TFT DT, and iselectrically connected to the source electrode 119 s through a contacthole CH formed in the first and second insulating layers 130 and 170.The first electrode E1 directly contacts the uneven layer 180 and thussubstantially has a shape according to the shape of the uneven layer180.

The first electrode E1 may be an anode of the light emitting element ED.The first electrode E1 may be made of a transparent conductive material,for example, a transparent conductive oxide such as ITO or IZO.

The light emitting layer EL is formed on the first electrode E1 anddirectly contacts the first electrode E1, and thus the light emittinglayer EL substantially has a shape according to the shape of the firstelectrode E1. Accordingly, the light emitting layer EL has a shapeaccording to the shape of the uneven layer 180.

The light emitting layer EL may include at least two light emittingportions to emit a white light. For example, the light emitting layer ELmay include a first light emitting portion and a second light emittingportion to emit a white light by a mixture of a first light and a secondlight. In this case, the first light emitting portion emits a firstlight and may include one of a blue light emitting portion, a greenlight emitting portion, a red light emitting portion, a yellow lightemitting portion and a yellow-green light emitting portion. The secondlight emitting portion may include another one, which emits a lighthaving a complementary color to the first light, out of a blue lightemitting portion, a green light emitting portion, a red light emittingportion, a yellow light emitting portion and a yellow-green lightemitting portion.

The second electrode E2 is formed on the light emitting layer EL anddirectly contacts the light emitting layer EL, and thus the secondelectrode E2 substantially has a shape according to the shape of thelight emitting layer EL. Accordingly, the second electrode E2 has ashape according to the shape of the uneven layer 180.

The second electrode E2 may be a cathode of the light emitting elementED. The second electrode E2 may include a metal material having a highreflectance to reflect a light from the light emitting layer EL towardthe substrate 100.

For example, the second electrode E2 may have a multiple-layeredstructure, such as a stacked structure with Al and Ti (e.g., Ti/Al/Ti),a stacked structure with Al and ITO (e.g., ITO/Al/ITO), an APC(Ag/Pd/Cu)alloy or a stacked structure with APC alloy and ITO (e.g., ITO/APC/ITO),or have a single-layered structure using Ag, Al, Mo, Au, Mg, Ca, Ba, oran alloy thereof.

The light emitting element ED emits a white light by an emission of thelight emitting layer EL according to a data signal supplied to the firstelectrode E1. The light emitting element ED has a shape according to theshape of the uneven layer 180. Accordingly, among a white light incidenton an interface between the first electrode E1 and the uneven layer 180,a light having an incident angle equal to or less than a critical angleof a total reflection is directly extracted to the substrate 100, and alight having an incidence angle greater than the critical angle changesin its traveling path by the furrow 181 and the wall 183 of the unevenlayer 180 and is then extracted to the substrate 100. Accordingly, inthis aspect, a light extraction efficiency of each pixel region canincrease.

The light emitting display device may further include a bank layer 190and an encapsulation layer 200.

The bank layer 190 defines the light emission region EA, and may beformed on an edge of the first electrode E1 and the second insulatinglayer 170. The bank layer 190 may be made of an organic material such asa benzocyclobutene (BCB) based resin, an acryl based resin, or apolyimide based resin. Alternatively, the bank layer 190 may be made ofa photosensitive material containing a black pigment, and in this case,the bank layer 190 serves as a light shielding member.

The light emitting layer EL and the second electrode E2 may be formed onthe bank layer 190. In other words, the light emitting layer EL may beformed on the substrate 100 having the first electrode E1 and the banklayer 190, and the second electrode E2 may be formed to cover the lightemitting layer EL.

The encapsulation layer 200 is formed on the substrate 100 to cover thesecond electrode E2 i.e., to cover all pixel regions. The encapsulationlayer 200 protects the TFTs and the light emitting element ED from anexternal impact, and prevents moisture permeating the light emittingelement ED.

Selectively, the encapsulation layer 200 may be replaced with a fillingmaterial surrounding all pixel regions, and in this case, the lightemitting display device may further include an encapsulation substrate300 that is adhered onto the substrate 100 through the filling material.The encapsulation substrate 300 may be made of a metal material.

Further, the light emitting display device of this aspect may include apolarizing film that is adhered on a bottom surface (or a lightextraction surface) of the substrate 100. The polarizing film changes anexternal light reflected by a TFT and/or a line formed in a pixel regioninto a circularly-polarized light and thus improves visibility andcontrast ratio.

In the light emitting display device of this aspect, by the uneven layer180 at the light emission region EA of the pixel region, a travelingpath of a light from the light emitting element ED changes thus a lightextraction efficiency can be improved, and thus a brightness can beimproved and a power consumption can be reduced. Further, since ashortest distance between the uneven layer 180 and the wavelengthconversion layer 150 is set to be 0.1 um or greater, the wavelengthconversion layer 150 being exposed directly to the furrow 181 can beprevented, and thus a property degradation of the light emitting elementED can be prevented.

FIG. 3 is a view enlarging a portion A of FIG. 2 to explain across-sectional structure of the uneven layer of this aspect. FIG. 4 isa plan view illustrating a plan structure of the uneven layer of FIG. 2.

Referring to FIGS. 2 to 4, the uneven layer 180 includes a plurality offurrows 181 and a wall 183 defining each furrow 181.

Each of the plurality of furrows 181 are provided concavely from a frontsurface 170 a of the second insulating layer 170 to have a regularinterval, and may be referred to as a concave portion or dent portion.

The furrows 181 may be arranged in a line along a first direction and bearranged in a zigzag shape along a second direction such that thefurrows 181 are located at regular intervals. In other words, while thefurrows 181 may be arranged in a lattice form having a regular interval,adjacent furrows 181 along a second direction may be arrangedalternately. Accordingly, centers of three adjacent furrows 181 may forma triangle shape TS.

The furrows 181 may substantially have the same depth with respect tothe front surface 170 a of the second insulating layer 170. Due to amanufacturing process error in a patterning process for the uneven layer180, a part of the furrows 181 may have a different depth.

A bottom surface (or lowest surface) 181 a of each furrow 181 isseparate at a predetermined distance from the wavelength conversionlayer 150. In other words, the bottom surface 181 a of the furrow 181faces a front surface 150 a of the wavelength conversion layer 150 withthe second insulating layer 170 therebetween. The second insulatinglayer 170 located between the bottom surface 181 a of the furrows 181and the wavelength conversion layer 150 may have a thickness of 0.1 umor greater in order that a part of the front surface 150 a of thewavelength conversion layer 150 being directly exposed to the furrows181 when forming the furrows 181 is prevented. When forming the furrows181, as the second insulating layer 170 between the bottom surface 181 aof the furrows 181 and the wavelength conversion layer 150 increases inthickness, a part of the front surface 150 a of the wavelengthconversion layer 150 being directly exposed to the furrows 181 iseffectively prevented, but in terms of a manufacturing process, amaterial cost and a process time of the second insulating layer 170 anda thickness of the light emitting display device increases. Accordingly,in order that the front surface 150 a of the wavelength conversion layer150 being directly exposed to the furrows 181 due to the depth of thefurrows 181 is prevented and also an increase of a material cost and aprocess time of the second insulating layer 170 and a thickness of thelight emitting display device is minimized, a maximum thickness of thesecond insulating layer 170 between the bottom surface 181 a of thefurrow 181 and the wavelength conversion layer 150 may be set to be 3 umor less. Thus, among the plurality of furrows 181, a shortest distanceL1 from the front surface 150 a of the wavelength conversion layer 150may be 0.1 um, and a longest distance from the front surface 150 a ofthe wavelength conversion layer 150 may be 3 um. As a result, a distanceL1 between the bottom surface 181 a of each furrow 181 and the frontsurface 150 a of the wavelength conversion layer 150 may be in a rangeof 0.1 um to 3 um.

In case that the shortest distance L1 is less than 0.1 um, in apatterning process for the uneven layer 180, a part of the front surface150 a of the wavelength conversion layer 150 may be removed thus dented,or may be directly exposed to the furrow 181. In cast that thewavelength conversion layer 150 is not covered by the second insulatinglayer 170 and is exposed to the furrow 181, a dark spot defect happensat a dented portion of the wavelength conversion layer 150, a moistureor the like by an outgassing of the wavelength conversion layer 150 isdiffused to the light emitting element ED thus property, reliability andlifetime of the light emitting element ED is reduced, the firstelectrode E1 is deteriorated due to the first electrode E1 directlycontacting the wavelength conversion layer 150, and the wavelengthconversion layer 150 is damaged by the deterioration of the firstelectrode E1. Thus, in case that the wavelength conversion layer 150 isnot covered by the second insulating layer 170 and is exposed to thefurrow 181, light emission property and lifetime of the light emittingdisplay device may be reduced.

In this aspect, when forming the uneven layer 180 in the secondinsulating layer 170 overlapping the light emission region EA, in orderto prevent a part of the front surface 150 a of the wavelengthconversion layer 150 being exposed to the furrow 181, the secondinsulating layer 170 is formed with a first layer (or first sub layer)170-1 and a second layer (or second sub layer) 170-2. In other words,using the same organic insulating material, the second insulating layer170 is configured with a double-layered structure that has two layers,formed sequentially, of different thicknesses.

The first layer 170-1 is formed to cover the first insulating layer 130and the wavelength conversion layer 150 and serves as an exposureprevention layer or sacrificial layer to prevent an exposure of thewavelength conversion layer 150. The first layer 170-1 is formed to havea thickness of 0.1 um to 3 um thus separate the bottom surface 181 a ofeach furrow 181 from the front surface 150 a of the wavelengthconversion layer 150 at a distance of 0.1 um to 3 um. Accordingly, whenforming the uneven layer 180, the front surface 150 a of the wavelengthconversion layer 150 being exposed directly to the furrow 181 isprevented.

The second layer 170-2 is formed to entirely cover the first layer 170-1and have a thickness greater than that of the first layer 170-1. Thesecond layer 170-2 provides a planarization layer on the first layer170-1 of the circuit region CA and the light emission region EA. Forexample, the second layer 170-2 has a thickness equal to or greater thana depth of the furrow 181 or a height H of the wall 183.

The second insulating layer 170 structurally includes the first layer170-1 and the second layer 170-2 in order to prevent an exposure of thefront surface 150 a of the wavelength conversion layer 150. However, thefirst layer 170-1 is formed through a first deposition process and afirst hardening process using an organic material, and then the secondlayer 170-2 is formed through a second deposition process and a secondhardening process using the same organic material. Accordingly, aboundary portion between the first layer 170-1 and the second layer170-2 of the double-layered structure formed on the circuit region CA ofthe substrate 100 may be not structurally distinguished.

The wall 183 surrounds each furrow 181 to define each furrow 181, andmay have a structure protruded in a convex shape on the wavelengthconversion layer 150. Accordingly, the wall 183 may have across-sectional structure of a convex lens shape or micro lens shape.The wall 183 changes a traveling path of a light, which is emitted fromthe light emitting element ED and is incident to the wall 183, towardthe substrate 100, and thus a light extraction efficiency of the pixelregion increases.

The wall 183 may have a hexagonal band shape in a plan view. One furrow181 may be placed in the hexagonal band shaped wall 183. Accordingly,the furrows 181 and the wall 183 on the light emission region EA form ahoneycomb structure of a hexagonal shape in a plan view. However, inthis aspect, it should be understood that the wall 183 defining onefurrow 181 may have a various shape in a plan view, for example, acircular band shape, an oval band shape, or polygonal band shape.

The wall 183 has a cross-sectional area that is alongside of (orparallel to) the wavelength conversion layer 150. In order to change atraveling path of an incident light and increase light extractionefficiency, the cross-sectional area of the wall 183 may become greateras the cross-section area may become closer to the wavelength conversionlayer 150. In other words, the wall 183 may decrease in width in anupward direction (i.e., in a direction from the substrate 100 to thelight emitting element ED).

The wall 183 may include a base surface portion 183 a, a top portion 183b, and a side surface portion 183 c.

The base surface portion 183 a may be defined as a bottom surface of thewall 183 close to the wavelength conversion layer 150. In other words,the base surface portion 183 a may be defined as a contact surfacebetween the first layer 170-1 overlapping the wavelength conversionlayer 150 and the wall 183, or a bottom surface of the wall 183contacting the front surface of the first layer 170-1.

A diameter (or width) D of the base surface portion 183 a may be setaccording to an aspect ratio (or height to width ratio) of the wall 183based on a height H of the wall 183 and the diameter D within a rangesuch that the base surface portion 183 a has a size greater than the topportion 183 b. The aspect ratio of the wall 183 may be defined as avalue that is the height H of the wall 183 divided by half the diameterD/2 of the base surface portion 183 a.

The base surface portions 183 a of adjacent walls 183 may be connectedto each other and form the bottom surface 181 a of the furrow 181. Inthis case, a pitch P between the adjacent walls 183 may be set to beequal to the diameter D.

Alternatively, the base surface portions 183 a of the adjacent walls 183may be separate from each other, and in this case, the bottom surface181 a of the furrow 181 may be the first layer 170-1 exposed between thebase surface portions 183 a of the adjacent walls 183. A pitch P betweenthe adjacent walls 183 is set to be greater than the diameter D, and thebase surface portions 183 a of adjacent walls 183 are separate from eachother with a gap therebetween.

In case that the gap is formed between the adjacent walls 183, whenforming the furrow 181, even though a misalign due to a deformation of aphoto mask happens, the uneven layer 180 can be formed without anexposure of the wavelength conversion layer 150, and thus a processmargin for the uneven layer 180 can increase.

The top portion 183 b is separate at a predetermined height from thebase surface portion 183 a. The top portion 183 b may be defined as apeak of the wall 183 having a convex shape. The top portion 183 b may belocated at the front surface 170 a of the second insulating layer 170 orlocated below the front surface 170 a.

The side surface portion 183 c is located between the base surfaceportion 183 a and the top portion 183 b.

The side surface portion 183 c may be formed in a curved shape betweenthe base surface portion 183 a and the top portion 183 b in order tochange a traveling path of an incident light thus increase a lightextraction efficiency. The side surface portion 183 c may have a curveshape with an inflection point IP in order to maximize a lightextraction efficiency. In this case, the side surface portion 183 c mayinclude an inflection portion IPP including the inflection point IP, afirst curved portion CP1 between the inflection portion IPP and the basesurface portion 183 a, and a second curved portion CP2 between theinflection portion IPP and the top portion 183 b.

The inflection portion IPP may include a concave portion between theinflection point IP and the first curved portion CP1 and a convexportion between the inflection point IP and the second curved portionCP2. Accordingly, a traveling path of a light incident on the inflectionportion IPP can change at various angles by each of the concave portionand the convex potion, and thus a light extraction efficiency of thepixel region can be improved.

The first curved portion CP1 may be formed in a concave shape betweenthe inflection portion IPP and the base surface portion 183 a. Thesecond curved portion CP2 may be formed in a convex shape between theinflection portion IPP and the top portion 183 b.

With respect to the height H of the wall 183, a ratio of a height h1 ofthe first curved portion CP1, a height h2 of the inflection portion IPPand a height h3 of the second curved portion CP2 may be set as, but notlimited to, 1:3:1, and the height h1 of the first curved portion CP1 andthe height h3 of the second curved portion CP2 may be equal to ordifferent from each other while the heights h1 and h3 are less than theheight h2 of the inflection portion IPP. Further, with respect to alength of the side surface portion 183 c, a curved length of theinflection portion IPP may be greater than that of each of the first andsecond curved portions CP1 and CP2, a curved length of the first curvedportion CP1 and a curved length of the second curved portion CP2 may beequal to or different from each other. The curved length of the secondcurved portion CP2 may be greater than that of the first curved portionCP1. The heights h1, h2 and h3 and the curved lengths of the firstcurved portion CP1, the inflection portion IPP and the second curvedportion CP2 may be determined according to the aspect ratio of the wall183 that is determined to improve a light extraction efficiencyaccording to a change of a light traveling path.

The inflection portion IPP, the first curved portion CP1 and the secondcurved portion CP2 of the side surface portion 183 c may have asymmetrical structure with respect to the top portion 183 b, and thusthe wall 183 may have a bell or Gaussian curve cross-sectionalstructure.

Alternatively, the side surface portion 183 c may have a concave orconvex curved shape such that the side surface portion 183 c has anycurvature between the base surface portion 183 a and the top portion 183b.

FIG. 5 is a view enlarging a portion A of FIG. 2 to explain across-sectional structure of the uneven layer and the light emittingelement of this aspect. FIG. 6 is a plan view illustrating emissionbrightness at the uneven layer of FIG. 2.

Referring to FIGS. 2, 5 and 6, the light emitting element ED includesthe first electrode E1, the light emitting layer EL and the secondelectrode E2 which are stacked sequentially. The light emitting elementED is formed to have a shape according to the shape of the furrows 181and the wall 183 of the second insulating layer 170, and thus atraveling path of a light from the light emitting element ED changestoward the substrate 100 by the uneven layer 180 and a light extractionefficiency can increase.

The light emitting element ED may have different thicknesses accordingto formation positions on the furrow 181 and the wall 183. In detail, ina process of forming the light emitting element ED using a depositionmethod, a deposition material of the light emitting element ED hasstraightness, and is deposited on the uneven layer 180 not on an evensurface. Accordingly, the light emitting element ED is formed on theuneven layer 180 to have a shape according to the shape of the furrow181 and the wall 183, and thus the light emitting element ED may havedifferent thicknesses T1, T2 and T3 at the furrow 181, the top portion183 b and the inflection portion IPP, respectively. In other words, eachof the bottom surface 181 a of the furrow 181 and the top portion 183 bhas a curvature greater than that of the inflection portion IPP, or hasa slope less than that of the inflection portion IPP with respect to thebase surface portion 183 a. Accordingly, the light emitting element EDmay have a first thickness T1 on the bottom surface 181 a of the furrow181, a second thickness T2, which is equal to or different from thefirst thickness T1, on the top portion 183 b, and a third thickness T3,which is less than each of the first and second thicknesses T1 and T2,on the inflection portion IPP.

In case that the light emitting layer EL is formed as an organic lightemitting layer, an emission of the light emitting layer EL is producedmostly at a region having a high current density. In the light emittingelement ED of this aspect, a relatively strong main emission is producedat the relatively thin light emitting layer EL of the third thickness T3on the inflection portion IPP, a first sub emission less than the mainemission is produced at the relatively thick light emitting layer EL ofthe first thickness T1 greater than the third thickness T3 on the bottomsurface 181 a of the furrow 181, and a second sub emission less than themain emission is produced at the relatively thick light emitting layerEL of the second thickness T2 greater than the third thickness T3 on thetop portion 183 b. According to the shape of the uneven layer 180, aregion where the main emission is produced may be defined as a mainlight extraction region, and a region where the sub emission is producedmay be defined as a sub light extraction region. Accordingly, as shownin FIG. 6, regarding brightness over the uneven layer 180, a regionoverlapping the inflection portion IPP has a relatively high brightness,and a region overlapping the bottom surface 181 a has a relatively lowbrightness.

Considering the thickness of the light emitting element ED formedaccording to the shape of the uneven layer 180, the top portion 183 b ofthe wall 183 may serve as a sub emission region and have a high lightextraction efficiency but a low current density. The bottom surface 181a of the furrow 181 may serve as a sub emission region and have a lowestlight extraction efficiency and a lowest current density. The inflectionportion IPP of the wall 183 may serve as a main emission region and havea high light extraction efficiency and a high current density.Accordingly, with respect to an emission amount of the light emittingelement ED per unit area, an emission amount on the inflection portionIPP may be relatively greatest, an emission amount on the bottom surface181 a may be relatively smallest, and an emission amount on the topportion 183 b may be equal to or greater than the emission amount on thebottom surface 181 a.

Accordingly, regarding the side surface portion 183 c of the wall 183,as a ratio occupied by the inflection portion IPP is greater, a lightextraction efficiency may be greater, and as a ratio occupied by thefirst curved portion CP1 is less, a power consumption may be less. Thus,since the wall 183 is configured such that a ratio (h1:h2:h3) the heighth1 of the first curved portion CP1, the height h2 of the inflectionportion IPP and the height h3 of the second curved portion CP2 is set as1:3:1 with respect to the height H of the wall 183, a light extractionefficiency can increase.

Through the shape of the uneven layer 180, a light extraction efficiencyis influenced by the aspect ratio of the wall 183 based on the height Hand the diameter D of the base surface portion 183 a. Accordingly, theaspect ratio of the wall 183 is determined in a range of 0.4 to 0.7 inorder to increase a light extraction efficiency.

The case that the aspect ratio of the wall 183 is in a range of 0.4 to0.7 has a light extraction efficiency greater than that of the case thatthe aspect ratio is below 0.4 or over 0.7. In other words, in case thatthe aspect ratio of the wall 183 is below 0.4, the height H of the wall183 is very low, thus an incident light from the light emitting elementED does not travel to the substrate but is trapped in the light emittingelement ED, and thus a light extraction efficiency is reduced. In casethat the aspect ratio of the wall 183 is over 0.7, the height H of thewall 183 is very high, thus an incident light from the light emittingelement ED does not travel to the substrate but is trapped in the wall183, and thus a light extraction efficiency is reduced. Particularly, incase that the aspect ratio is over 0.7, there is a tendency for anenhancement of a current efficiency of the light emitting element ED tobe reduced, and in case that the aspect ratio is in a range of 0.4 to0.7, a current efficiency enhancement of the light emitting element EDbecomes a maximum value. Thus, it is preferable that the aspect ratio ofthe wall 183 is set in a range of 0.4 to 0.7 in order to maximize alight extraction efficiency of the pixel region.

In case that the aspect ratio of the wall 183 is in a range of 0.4 to0.7, the diameter D of the base surface portion 183 a may be set in arange of 4 um to 12 um based on a resolution of a mask to form theuneven layer 180. When the diameter D of the base surface portion 183 ais 4 um and the height H of the wall 183 is 0.8um, the wall 183 has theaspect ratio of 0.4. When the diameter D of the base surface portion 183a is 12 um and the height H of the wall 183 is 4.2 um, the wall 183 hasthe aspect ratio of 0.7. In case that the height H of the wall 13 isbelow 0.8, the aspect ratio is reduced thus a current efficiencyenhancement may be reduced, and an amount of a light, emitted from thelight emitting element ED, multiple reflected by the wall 183 increasesthus an amount of a light extracted to the substrate is reduced. In casethat the height H of the wall is over 4.2, the aspect ratio increasesthus a current efficiency enhancement may be reduced.

Accordingly, in this aspect, in order for the aspect ratio of the wall183 to be in a range of 0.4 to 0.7, the diameter D of the base surfaceportion 183 a is set in a range of 4 um to 12 um and the height H of thewall 183 is set in a range of 0.8 um to 4.2 um, and thus a lightextraction efficiency of the pixel region can be maximized.

Further, a full width at half maximum (or a full width at half height) Fof the wall 183 may be set in a range of 1 um to 2.5 um. The full widthat half maximum F means a full width at half a height (2/H) of the wall183. In case that the full width at half maximum F of the wall 183 isbelow 1 um or over 2.5 um, a light extraction efficiency by the wall 183may be reduced. In case that the full width at half maximum F of thewall 183 is below 1 um, an amount of a light, from the light emittingelement ED, reflected by the wall 183 and then extracted to thesubstrate is less than an amount of a light diffuse reflected at thewall 183, thus an amount of a light trapped in the light emittingelement ED increases and thus a light extraction efficiency may bereduced.

Particularly, a light, which has an incidence angle less than a criticalangle of a total reflection, out of a light emitted from the lightemitting element ED may be extracted to the outside of the substratethrough a multiple reflection between the side surface portions 183 c ofthe wall 183. In case that the full width at half maximum F of the wall183 exceeds 2.5 um, an amount of a light reflected between the sidesurface portions 183 c is reduced and thus an amount of a light outputto the outside of the substrate is reduced.

In this aspect, by raising a ratio occupied by the inflection portionIPP that becomes a main emission region, out of regions of the wall 183formed at the uneven layer 180, due to a thin thickness of the lightemitting element ED, an extraction efficiency of a light emitted fromthe light emitting element ED can increase. Further, by the aspect ratioof the wall 183 being set in a range of 0.4 to 0.7, a current efficiencyenhancement is raised and thus a power consumption can be reduced.Further, by the full width at half maximum F of the wall 183 being setin a range of 1 um to 2.5 um, an extraction efficiency of a lightemitted from the light emitting element ED can increase. As a result, alight extraction efficiency of each pixel region can increase.

FIG. 7 is a cross-sectional view illustrating the pixel region accordingto the first aspect of the present disclosure. FIG. 8 is a viewillustrating a cross-sectional structure of the uneven layer at aportion B of FIG. 7. The light emitting display device of FIGS. 7 and 8further includes a barrier layer 160 in the pixel region. For thepurpose of explanations, a barrier layer and relevant components areexplained below, and explanations of the similar or same parts describedabove may be omitted.

Referring to FIGS. 7 and 8, the barrier layer 160 is formed to cover thewavelength conversion layer 150. In other words, the barrier layer 160is provided between the uneven layer 180 and the wavelength conversionlayer 150. Further, the barrier layer 160 covers a front surface 150 aand side surfaces of the wavelength conversion layer 150 and the firstinsulating layer 130 at the light emission region EA and the circuitregion CA. Accordingly, the barrier layer 160 overlapping the wavelengthconversion layer 150 is between the bottom surface 181 a of the furrows181 and the wavelength conversion layer 150, and is between the basesurface portion 183 a of the wall 183 and the wavelength conversionlayer 150. Further, the barrier layer 160 not overlapping the wavelengthconversion layer 150 is between the first insulating layer 130 and thesecond insulating layer 170. The barrier layer 160 serves as an etchstopper on the wavelength conversion layer 150 when forming the unevenlayer 180, thus the wavelength conversion layer 150 being exposeddirectly to the furrow 181 is prevented, and thus a problem by anexposure of the wavelength conversion layer 150 is fundamentallyprevented.

The barrier layer 160 may have a thickness t1 that corresponds to theshortest distance L1 between the bottom surface 181 a of the furrows 181and the wavelength conversion layer 150. In other words, the barrierlayer 160 may be formed at the thickness t1 of 0.1 um to 3 um to preventthe wavelength conversion layer 150 being exposed to the furrow 181 whenforming the uneven layer 180.

In case that the barrier layer 160 has the thickness t1 less than 0.1um, wavelength conversion particles in the wavelength conversion layer150 penetrates the barrier layer 160 and damages the light emittingelement ED. Further, as the thickness t1 of the barrier layer 160increases, an exposure of the wavelength conversion layer 150 isprevented effectively, but in terms of a manufacturing process, amaterial cost and a process time of the barrier layer 160 and athickness of the light emitting display device increases. Accordingly,in order that when forming the uneven layer 180, the barrier layer 160serves as an etch stopper on the wavelength conversion layer 150 andalso an increase of a material cost and a process time of the barrierlayer 160 and a thickness of the light emitting display device isminimized, the barrier layer 160 is preferably formed to have thethickness t1 of 0.1 um to 3 um. For example, in case that the wavelengthconversion particle of the wavelength conversion layer 150 has a sizeless than 0.1 um, the barrier layer 160 may be formed to have thethickness t1 of at least 0.1 um.

The barrier layer 160 may be formed of a material not removed by adeveloping material (or an etching material) that is used in apatterning process of the second insulating layer 170.

Alternatively, the barrier layer 160 may be formed of an inorganicmaterial, for example, silicon oxide or silicon nitride. In other words,the barrier layer 160 may be formed of the same material as the firstinsulating layer 130, and in this case, the barrier layer 160 and thefirst insulating layer 130 may be formed of silicon oxide.

After forming the uneven layer 180, a process of forming the contacthole CH exposing a part of the source electrode 119 s of the driving TFTDT may be conducted. Considering the forming process of the contact holeCH, in case that the barrier layer 160 is made of the same material asthe first insulating layer 130, the contact hole CH can be formed in thebarrier layer 160 and the first insulating layer 130 through onepattering process. Accordingly, to simplify manufacturing processes ofthe light emitting display device, the barrier layer 160 is preferablymade of the same material as the first insulating layer 130.

In the light emitting display device of this aspect, by the uneven layer180 at the light emission region EA of the pixel region, a travelingpath of a light from the light emitting element ED changes thus a lightextraction efficiency can be improved, and thus a brightness can beimproved and a power consumption can be reduced.

Further, since the barrier layer 160 is formed as an etch stopperbetween the uneven layer 180 and the wavelength conversion layer 150,the wavelength conversion layer 150 being exposed directly to the furrow181 can be prevented, and thus a property degradation of the lightemitting element ED can be prevented.

FIG. 9 is a view enlarging a portion B of FIG. 7. In FIG. 9, it is shownthat a structure of furrows 181 of the uneven layer 180 is modified. Forthe purpose of explanations, the furrows 181 and relevant components areexplained below, and explanations of the similar or same parts describedabove may be omitted.

Referring to FIGS. 7 and 9, the uneven layer 180 includes a plurality offurrows 181 and a wall 183 defining each of the plurality of furrows181. The uneven layer 180 may be equal to the uneven layer shown inFIGS. 2 to 4, except for the bottom surface 181 a of each furrow 181.

The furrows 181 and the wall 183 of the uneven layer 180 may be formedthrough a selective light-exposure process and a developing process ofthe second insulating layer 170 using a mask. When an light-exposureamount for the bottom surface 181 a of the furrows 181 increases by amisalign due to a deformation of a photo mask in the light-exposureprocess, the second insulating layer 170 is fully removed at the bottomsurface 181 a of the furrows 181, and thus the base surface portions 183a of the adjacent walls 183 may be separate at a constant gap G fromeach other. If the barrier layer 160 is not formed between the unevenlayer 180 and the wavelength conversion layer 150 and the gap G isformed between the base surface portions 183 a of the adjacent walls183, the wavelength conversion layer 150 is directly exposed to thefurrow 181.

However, in this aspect, since the barrier layer 160 is formed betweenthe uneven layer 180 and the wavelength conversion layer 150, when thegap G is formed between the base surface portions 183 a of the adjacentwalls 183, the wavelength conversion layer 150 is not directly exposedto the furrow 181 by the barrier layer 160.

Further, since the gap G between the adjacent walls 183 forms the bottomsurface 181 a of the furrows 181 and the light emitting element EDformed on the bottom surface 181 a of the furrows 181 serves as a subemission region, this configuration does not have a great effect on alight extraction efficiency. Accordingly, whether the gap G is formed ornot almost makes no difference of light extraction efficiency of eachpixel region.

Thus, a light extraction efficiency can increase by forming the gap Gbetween the adjacent walls 183, and particularly, even though a misaligndue to a deformation of a photo mask happens, the uneven layer 180 canbe formed without an exposure of the wavelength conversion layer 150,and thus a process margin for the uneven layer 180 can increase.

FIG. 10 is a cross-sectional view illustrating a pixel region of a lightemitting display device according to a second aspect of the presentdisclosure.

The light emitting display device 10 may be a top emission type displaydevice or bottom emission type display device according to atransmission direction (or output direction) of an emitted light. Inthis aspect, a bottom emission type light emitting display device 10 isdescribed by way of example.

Referring to FIG. 10, the pixel region SP may include a light emissionregion EA in which a light emitting element ED is formed and throughwhich an image is substantially displayed, and a circuit region CA whichis located around edges of the light emission region EA and in which adriving TFT DT is formed.

In the light emitting display device 10, a substrate 401 having thedriving TFT DT and a light emitting element ED may be encapsulated by aprotection film 402.

An active layer 405 is formed in the circuit region CA. The active layer405 may be made of silicon, and includes a channel region 405 a at acenter of the active layer 405, and drain and source regions 405 b and405 c that are located at both sides of the channel regions 405 a andare highly doped with impurities.

A gate insulating layer 406 is located on the active layer 405.

The gate insulating layer 406 is formed on the channel region 405 a ofthe active layer 405. The gate insulating layer 406 may not be formedover an entire surface of the substrate 401, may be formed in an islandshape only on the channel region 405 a.

A gate electrode 407 is formed on the gate insulating layer 406corresponding to the channel region 405 a, and even though not shown inthe drawings, a gate line extending along a direction is formed on thegate insulating layer 406.

A passivation layer 408 is formed on the gate electrode 407 and the gateline. In the passivation layer 408, first and second contact holes (orfirst and second active layer contact holes) CH1 are formed to exposethe drain and source regions 405 b and 405 c, respectively.

A drain electrode 410 a and a source electrode 410 b are formed on thepassivation layer 408, and contact the drain region 405 b and the sourceregion 405 c through the first and second contact holes CH1,respectively.

A first insulating layer 412 is located on the drain and sourceelectrodes 410 a and 410 b and the passivation layer 408 exposed betweenthe drain and source electrodes 410 a and 410 b.

The drain and source electrodes 410 a and 410 b, the active layer 405,the gate insulating layer 406 on the active layer 405, and the gateelectrode 407 form the driving TFT DT.

Even though not shown in the drawings, a data line crossing the gateline to define the pixel region SP is formed at the same layer as thedrain and source electrodes 410 a and 410 b, and a switching TFT mayhave the same structure as the driving TFT DT and be connected to thedriving TFT DT.

The driving TFT DT and the switching TFT are described to have a topgate type with a polycrystalline silicon or oxide semiconductor materialby way of example. Alternatively, the driving TFT DT and the switchingTFT may have a bottom gate type with amorphous silicon.

The substrate 401 may be usually formed of a glass material, andalternatively, may be formed of a transparent plastic material having abendable or flexible property, for example, polyimide material. In casethat the plastic material is used for the substrate 401, consideringthat a deposition at high temperature is conducted, polyimide having anexcellent heat-resisting property may be used an entire surface of thesubstrate 401 may be covered by at least one buffer layer 403.

The driving TFT DT may have a property of a threshold voltage beingshifted by a light, and to prevent this, the light emitting displaydevice 10 of this aspect may further include a light shielding layer 404located below the active layer 405.

The light shielding layer 404 is formed between the substrate 401 andthe active layer 405 and shields the active layer 405 from a lightincident toward the active layer 405 through the substrate 401, and thusa threshold voltage change of a TFT by an external light is prevented.The light shielding layer 404 may be covered by the buffer layer 403.

A wavelength conversion layer 414 is located on the first insulatinglayer 412 corresponding to the light emission region EA of each pixelregion SP.

In other words, the wavelength conversion layer 414 is supported by thefirst insulating layer 412 and is covered by a second insulating layer416 so that the wavelength conversion layer 414 is located between thefirst insulating layer 412 and an uneven layer 420 and overlaps thelight emitting element ED.

The wavelength conversion layer 414 may include a color filter thattransmits a wavelength of a color light, which is set (or defined) atits pixel region SP, out of a white light emitted from the lightemitting element ED toward the substrate 401.

Alternatively, the wavelength conversion layer 414 may transmits awavelength of red, green or blue. For example, in the light emittingdisplay device 10, one unit pixel may consist of neighboring first tothird pixel regions SP, and in this case, a wavelength conversion layer414 of the first pixel region may include a red color filter, awavelength conversion layer 414 of the second pixel region may include agreen color filter, and a wavelength conversion layer 414 of the thirdpixel region may include a blue color filter.

Further, in the light emitting display device 10, one unit pixel mayinclude a white pixel region that has no wavelength conversion layer.

Alternatively, the wavelength conversion layer 414 may include a quantumdot that has a size to re-emit according to a white light emitted fromthe light emitting element ED toward the substrate 401 and output alight of a color set at its pixel region SP. The quantum dot may beformed of CdS, CdSe, CdTe, ZnS, ZnSe, CdZnSeS, GaAs, GaP, GaAs—P, Ga—Sb,InAs, InP, InSb, AlAs, AlP or AlSb.

For example, a wavelength conversion layer 414 of a first pixel regionmay include a quantum dot of CdSe or InP, a wavelength conversion layer414 of a second pixel region may include a quantum dot of CdZnSeS, awavelength conversion layer 414 of a third pixel region may include aquantum dot of ZnSe. The light emitting display device 10 using thewavelength conversion layer 414 with a quantum dot can have a high colorreproduction range.

Alternatively, the wavelength conversion layer 414 may be formed of acolor filter containing a quantum dot.

The second insulating layer 416 is formed on the wavelength conversionlayer 414. The second insulating layer 416 has a drain contact hole CH2,which exposes the source electrode 410 b, along with the firstinsulating layer 412.

The uneven layer 420 may be located at an upper portion of the secondinsulating layer 416, and changes a traveling path of a light emittedfrom the light emitting element ED, and thus increases a lightextraction efficiency of the pixel region SP.

The uneven layer 420 includes a plurality of furrows 418 located betweenthe light emitting element ED and the wavelength conversion layer 414.In other words, the uneven layer 420 may include a plurality of furrows418 and a wall 419.

Each of the plurality of furrow 418 is formed concavely from a frontsurface (or top surface) 416 a of the second insulating layer 416. Withrespect to the front surface 416 a of the second insulating layer 416,each of the plurality of furrows 418 may have the same depth.

A bottom surface (or lowest surface) of each furrow 418 is separate at apredetermined distance from the wavelength conversion layer 414. Inorder that a front surface of the wavelength conversion layer 414 beingdirectly exposed to the furrows 418 due to the depth of the furrows 418is prevented, a shortest distance from the bottom surface of the furrows418 to the wavelength conversion layer 414 may be 0.1 um or greater.

In this case, the second insulating layer 416 between the bottom surfaceof the furrows 418 and the wavelength conversion layer 414 may have athickness of 0.1 um or greater.

In case that the second insulating layer 416 between the bottom surfaceof the furrows 418 and the wavelength conversion layer 414 has athickness less than 0.1 um, in a patterning process for the uneven layer420, a part of the wavelength conversion layer 414 may be directlyexposed to the furrow 418, and thus a property of the light emittingelement ED formed on the uneven layer 420 may be deteriorated.

The wall 419 may have a structure to define or surround each furrow 418.The wall 419 changes a traveling path of a light from the light emittingelement ED toward substrate 401 and increases an extraction efficiencyof a light from the light emitting element ED.

The wall 419 may include a base surface portion (419 a of FIG. 11), atop portion (419 b of FIG. 11), and a side surface portion (419 c ofFIG. 11). In the uneven layer 420 of this aspect, the base surfaceportions of the adjacent walls 419 are separate at a gap G from eachother.

In case that the gap G is formed between the adjacent walls 419, eventhough a misalign due to a deformation of a photo mask happens whenforming the furrows 418, the uneven layer 420 can be formed without anexposure of the wavelength conversion layer 414, and thus a processmargin for the uneven layer 420 can increase.

In the light emitting display device 10 of this aspect, since an optimumcondition for the uneven layer 420 with the gap G is provided, anextraction efficiency of a light emitted from the light emitting elementED can be further improved. This is explained below in detail.

A first electrode E1 is located on the uneven layer 420. The firstelectrode E1 is connected to the source electrode 410 b of the drivingTFT DT, and may be made of a material having a relatively high workfunction and serve as an anode.

For example, the first electrode E1 may be made of a metal oxidematerial such as ITO or IZO, a mixture of a metal and an oxide materialsuch as ZnO:Al and SnO₂:Sb , or a conductive polymer such asPoly(3-methylthiophene), Poly[3,4-(ethylene-1,2)-thiophene] (PEDT),polypyrrole and polyaniline. Alternatively, the first electrode E1 maybe formed of a carbon nano tube (CNT), graphene, or a silver nano wire.

The first electrode E1 is located at each pixel regions SP, and a bank421 is located between the adjacent first electrodes E1. In other words,the first electrodes E1 are separate from each other with the bank 421as a boundary portion of each pixel region SP.

A light emitting layer EL e.g., an organic light emitting layer EL islocated on the first electrode E1, and further the organic lightemitting layer EL may be located on the bank 421. The organic lightemitting layer EL may be formed with a single layer made of an emittingmaterial, and alternatively, the organic light emitting layer EL may beformed with a multiple layers that may include a hole injection layer, ahole transport layer, an emitting material layer, an electron transportlayer and an electron injection layer.

A second electrode E2 is located on the organic light emitting layer ELand may serve as a cathode.

The second electrode E2 may be made of a material having a relativelylow work function. The second electrode E2 may be formed with a singlelayer or multiple layers using a first metal such as Ag and a secondmetal such as Mg, and the single layer may be made of an alloy of thefirst and second metals at a predetermined ratio thereof.

When the first electrode E1 and the second electrode E2 are applied withrespective voltages, a hole from the first electrode E1 and an electronfrom the second electrode E2 are transported to the organic lightemitting layer EL and form an exciton, and when a transition of theexciton from an excited state to a ground state happens, a light isproduced and emitted.

The emitted light passes through the first electrode E1 and travels tothe outside, and thus the light emitting display device 10 displays animage.

All of the first electrode E1, the organic light emitting layer EL andthe second electrode E2 are formed along the furrow 418 and the wall 419of the uneven layer 420 and have a shape according to the shape of theuneven layer 420.

The protection film 402 in a thin film type is formed on the driving TFTDT and the light emitting element ED with an encapsulation layer 423therebetween, and thus the light emitting display device 10 isencapsulated.

The encapsulation layer 423 is formed on the substrate 401 to cover thesecond electrode E2 i.e., to cover all pixel regions SP. Theencapsulation layer 423 protects the driving TFT DT and the lightemitting element ED from an external impact, and prevents moisturepermeating the light emitting element ED.

Further, the light emitting display device 10 of this aspect may includea polarizing plate (or polarizing film) on a surface, through which anemitted light transmits, of the substrate 401 to prevent a reduction ofcontrast due to an external light.

In other words, the polarizing plate is located at the light-emittingsurface and prevents an external light, which is reflected inside thedisplay device 10, from going back to the outside, and thus the contrastcan be improved.

In the light emitting display device 10 of this aspect, by the unevenlayer 420 at the light emission region EA of the pixel region SP, atraveling path of a light from the light emitting element ED changesthus a light extraction efficiency can be improved, and thus abrightness can be improved and a power consumption can be reduced.

Further, since a shortest distance between the uneven layer 420 and thewavelength conversion layer 414 is set to be 0.1 um or greater, thewavelength conversion layer 414 being exposed directly to the furrow 418can be prevented, and thus a property degradation of the light emittingelement ED can be prevented.

Particularly, since an optimum condition for the uneven layer 420 withthe gap G is provided, an extraction efficiency of a light emitted fromthe light emitting element ED can be further improved.

FIG. 11 is a view enlarging a portion A of FIG. 10 to explain across-sectional structure of the uneven layer of this aspect.

FIG. 12 is a graph illustrating a relation between an aspect ratio A/Rand a current efficiency enhancement for various aspect ratios of awall. FIG. 13 is a graph illustrating a brightness efficiency accordingto a relation between an aspect ratio at half maximum F_AR and an aspectratio at half maximum over an aspect ratio Rm of a wall.

Referring to FIG. 11, the uneven layer 420 includes a plurality offurrows 418 and a wall 419 defining each furrow 418.

Each of the plurality of furrows 418 are provided concavely from a frontsurface 416 a of the second insulating layer 416 to have a regularinterval, and may be referred to as a concave portion or dent portion.

The furrows 418 may substantially have the same depth with respect tothe front surface 416 a of the second insulating layer 416. A bottomsurface (or lowest surface) 418 a of each furrow 418 is separate at apredetermined distance from the wavelength conversion layer 414.

In other words, the bottom surface 418 a of the furrow 418 faces a frontsurface 414 a of the wavelength conversion layer 414 with the secondinsulating layer 416 therebetween. The second insulating layer 416located between the bottom surface 418 a of the furrows 418 and thewavelength conversion layer 414 may have a thickness of 0.1 um orgreater in order that a part of the front surface 414 a of thewavelength conversion layer 414 being directly exposed to the furrows418 when forming the furrows 418 is prevented.

When forming the furrows 418, as the second insulating layer 416 betweenthe bottom surface 418 a of the furrows 418 and the wavelengthconversion layer 414 increases in thickness, a part of the front surface414 a of the wavelength conversion layer 414 being directly exposed tothe furrows 418 is effectively prevented, but in terms of amanufacturing process, a material cost and a process time of the secondinsulating layer 416 and a thickness of the light emitting displaydevice increases.

Accordingly, in order that the front surface 414 a of the wavelengthconversion layer 414 being directly exposed to the furrows 418 due tothe depth of the furrows 418 is prevented and also an increase of amaterial cost and a process time of the second insulating layer 416 anda thickness of the light emitting display device is minimized, a maximumthickness of the second insulating layer 416 between the bottom surface418 a of the furrow 418 and the wavelength conversion layer 414 may beset to be 3 um or less.

Thus, among the plurality of furrows 418, a shortest distance L1 fromthe front surface 414 a of the wavelength conversion layer 414 may be0.1 um, and a longest distance from the front surface 414 a of thewavelength conversion layer 414 may be 3 um. As a result, a distance L1between the bottom surface 418 a of each furrow 418 and the frontsurface 414 a of the wavelength conversion layer 414 may be in a rangeof 0.1 um to 3 um.

In case that the shortest distance L1 is less than 0.1 um, in apatterning process for the uneven layer 420, a part of the front surface414 a of the wavelength conversion layer 414 may be removed thus dented,or may be directly exposed to the furrow 418.

In cast that the wavelength conversion layer 414 is not covered by thesecond insulating layer 416 and is exposed to the furrow 418, a darkspot defect happens at a dented portion of the wavelength conversionlayer 414, a moisture or the like by an outgassing of the wavelengthconversion layer 414 is diffused to the light emitting element ED thusproperty, reliability and lifetime of the light emitting element ED isreduced, the first electrode E1 is deteriorated due to the firstelectrode E1 directly contacting the wavelength conversion layer 414,and the wavelength conversion layer 414 is damaged by the deteriorationof the first electrode E1.

Thus, in case that the wavelength conversion layer 414 is not covered bythe second insulating layer 416 and is exposed to the furrow 418, lightemission property and lifetime of the light emitting display device maybe reduced.

In this aspect, in terms of a manufacturing process, considering amaterial cost and a process time of the second insulating layer 416 andthe like, the second insulating layer 416 is formed with a first layer(or first sub layer) 416-1 and a second layer (or second sub layer)416-2 in order to secure the shortest distance L1 between the furrows418 and the front surface 414 a of the wavelength conversion layer 414.

In other words, using the same organic insulating material, the secondinsulating layer 416 is configured with a double-layered structure thathas two layers, formed sequentially, of different thicknesses.

The first layer 416-1 is formed to cover the first insulating layer 412and the wavelength conversion layer 414 and serves as an exposureprevention layer or sacrificial layer to prevent an exposure of thewavelength conversion layer 414.

The first layer 416-1 is formed to have a thickness of 0.1 um to 3 umthus separate the bottom surface 418 a of each furrow 418 from the frontsurface 414 a of the wavelength conversion layer 414 at a distance of0.1 um to 3 um. Accordingly, when forming the uneven layer 420, thefront surface 414 a of the wavelength conversion layer 414 being exposeddirectly to the furrow 418 is prevented.

The second layer 416-2 is formed to entirely cover the first layer 416-1and have a thickness greater than that of the first layer 416-1. Thesecond layer 416-2 provides a planarization layer on the first layer416-1 of the circuit region CA and the light emission region EA. Forexample, the second layer 416-2 has a thickness equal to or greater thana depth of the furrow 418 or a height H of the wall 419.

The second insulating layer 416 structurally includes the first layer416-1 and the second layer 416-2 in order to prevent an exposure of thefront surface 414 a of the wavelength conversion layer 414. However, thefirst layer 416-1 is formed through a first deposition process and afirst hardening process using an organic material, and then the secondlayer 416-2 is formed through a second deposition process and a secondhardening process using the same organic material.

Accordingly, a boundary portion between the first layer 416-1 and thesecond layer 416-2 of the double-layered structure formed on the circuitregion CA of the substrate 401 may be not structurally distinguished.

The wall 419 surrounds each furrow 418 to define each furrow 418, andmay have a structure protruded in a convex shape on the wavelengthconversion layer 414.

Accordingly, the wall 419 may have a cross-sectional structure of aconvex lens shape or micro lens shape. The wall 419 changes a travelingpath of a light, which is emitted from the light emitting element ED andis incident to the wall 419, toward the substrate 401, and thus a lightextraction efficiency of the pixel region SP increases.

The wall 419 may have a hexagonal band shape in a plan view. One furrow418 may be placed in the hexagonal band shaped wall 419. Accordingly,the furrows 418 and the wall 419 on the light emission region EA form ahoneycomb structure of a hexagonal shape in a plan view. However, inthis aspect, the wall 419 defining one furrow 418 may have a variousshape in a plan view, for example, a circular band shape, an oval bandshape, or a polygonal band shape.

The wall 419 has a cross-sectional area that is alongside of (orparallel to) the wavelength conversion layer 414. In order to change atraveling path of an incident light and increase a light extractionefficiency, the cross-sectional area of the wall 419 may become greateras the cross-section area may become closer to the wavelength conversionlayer 414. In other words, the wall 419 may decrease in width in anupward direction (i.e., in a direction from the substrate 401 to thelight emitting element ED).

The wall 419 may include a base surface portion 419 a, a top portion 419b, and a side surface portion 419 c.

The base surface portion 419 a may be defined as a bottom surface of thewall 419 close to the wavelength conversion layer 414. In other words,the base surface portion 419 a may be defined as a contact surfacebetween the first layer 416-1 overlapping the wavelength conversionlayer 414 and the wall 419, or a bottom surface of the wall 419contacting the front surface of the first layer 416-1.

The base surface portion 419 a of the wall 419 is separate from adjacent(or neighboring) base surface portion 419 a to form the gap G, and inthis case, the bottom surface 418 a of the furrow 418 may be the secondlayer 416-1 exposed between the adjacent base surface portions 419 a.

A pitch between the adjacent walls 419 is set greater than a diameter(or width) D of the base surface portion 419 a, and the base surfaceportions 419 a of the adjacent walls 419 are separate at the gap G fromeach other.

In case that the gap G is formed between the adjacent walls 419, whenforming the furrow 418, even though a misalign due to a deformation of aphoto mask happens, the uneven layer 420 can be formed without anexposure of the wavelength conversion layer 414, and thus a processmargin for the uneven layer 420 can increase.

The top portion 419 b is separate at a predetermined height from thebase surface portion 419 a. The top portion 419 b may be defined as apeak of the wall 419 having a convex shape. The top portion 419 b may belocated at the front surface 416 a of the second insulating layer 416 orlocated below the front surface 416 a.

The side surface portion 419 c is located between the base surfaceportion 419 a and the top portion 419 b.

The side surface portion 419 c may be formed in a curved shape betweenthe base surface portion 419 a and the top portion 419 b in order tochange a traveling path of an incident light thus increase a lightextraction efficiency of the pixel region SP. The side surface portion419 c may have a curve shape with an inflection point IP in order tomaximize a light extraction efficiency of the pixel region SP.

In this case, the side surface portion 419 c may include an inflectionportion IPP including the inflection point IP, a first curved portionCP1 between the inflection portion IPP and the base surface portion 419a, and a second curved portion CP2 between the inflection portion IPPand the top portion 419 b.

The inflection portion IPP may include a concave portion between theinflection point IP and the first curved portion CP1 and a convexportion between the inflection point IP and the second curved portionCP2. Accordingly, a traveling path of a light incident on the inflectionportion IPP can change at various angles by each of the concave portionand the convex potion, and thus a light extraction efficiency of thepixel region SP can be improved.

The first curved portion CP1 may be formed in a concave shape betweenthe inflection portion IPP and the base surface portion 419 a. Thesecond curved portion CP2 may be formed in a convex shape between theinflection portion IPP and the top portion 419 b.

Accordingly, regarding the side surface portion 419 c of the wall 419,as a ratio occupied by the inflection portion IPP is greater, a lightextraction efficiency may be greater, and as a ratio occupied by thefirst curved portion CP1 is less, a power consumption may be less.

Thus, since the wall 419 is configured such that a ratio (h1:h2:h3) theheight h1 of the first curved portion CP1, the height h2 of theinflection portion IPP and the height h3 of the second curved portionCP2 is set as 1:3:1 with respect to the height H of the wall 419, alight extraction efficiency can increase.

The curved length of the second portion CP2 may be greater than that ofthe first curved portion CP1. The heights h1, h2 and h3 and the curvedlengths of the first curved portion CP1, the inflection portion IPP andthe second curved portion CP2 may be determined according to the aspectratio (A/R) of the wall 183 that is determined to improve a lightextraction efficiency according to a change of a light traveling path.

The inflection portion IPP, the first curved portion CP1 and the secondcurved portion CP2 of the side surface portion 419 c may have asymmetrical structure with respect to the top portion 419 b, and thusthe wall 419 may have a bell or Gaussian curve cross-sectionalstructure.

Alternatively, the side surface portion 419 c may have a concave orconvex curved shape such that the side surface portion 419 c has anycurvature between the base surface portion 419 a and the top portion 419b.

A light traveling path change due to the shape of the wall 419 causes animprovement of a light extraction efficiency, and variables (or factors)to determine the shape may include a diameter D, a height H, an aspectratio A/R, a full width at half maximum F, an aspect ratio at halfmaximum F_A/R, a slope S, a gap G, and an aspect ratio at half maximumover an aspect ratio Rm regarding the wall 419.

The aspect ratio A/R is defined as a following formula 1.

A/R=H/(D/2)   Formula 1

In other words, the aspect ratio A/R is the height H divided by half thediameter D/2.

In this aspect, according to forming the gap G between the adjacentwalls 419, the aspect ratio A/R of the wall 419 is set in a range of 0.5to 1.0.

In this regard, the gap G between the base surface portions 419 a of theadjacent walls 419 may be in a range of 0.3 um to 1.0 um.

In other words, when the gap G may be in a range of 0.3 um to 1.0 um, incase that the aspect ratio A/R is below 0.5, the height H of the wall419 is very low, thus an incident light from the light emitting elementED does not travel to the substrate 401 but is trapped in the lightemitting element ED, and thus a light extraction efficiency is reduced.

In case that the aspect ratio is over 1.0, the height H of the wall 419is very high, thus an incident light from the light emitting element EDdoes not travel to the substrate 401 but is trapped in the wall 419, andthus a light extraction efficiency is reduced.

Particularly, in case that the aspect ratio is over 1.0, there is atendency for a current efficiency enhancement of the light emittingelement ED to be reduced, and in case that the aspect ratio is in arange of 0.5 to 1.0, a current efficiency enhancement of the lightemitting element ED becomes a maximum value.

Thus, it is preferable that the aspect ratio of the wall 419 is set in arange of 0.5 to 1.0 in order to maximize a light extraction efficiencyof the pixel region SP.

In FIG. 12, a current efficiency enhancement being greater means a lightemission efficiency being better.

Referring to FIG. 12, when an aspect ratio A/R of the wall 419 is set ina range of 0.5 to 1.0, a current efficiency enhancement is high with 35cd/A or greater.

However, even when an aspect ratio A/R as one variable to define a shapeof the wall 419 is equal but other variables such as a full width athalf maximum F of the wall 419, a gap G between the walls 419 and thelike alters, a shape of the wall 419 alters.

Accordingly, in this aspect, an aspect ratio at half maximum F_A/R ofthe wall 419 is set in a range of 0.4 to 0.8, and an aspect ratio athalf maximum F_A/R over an aspect ratio A/R, Rm of the wall 419 is setin a range of 0.7 to 1.0. Further, a slope S of the wall is set in arange of 40 to 80 degrees.

The aspect ratio at half maximum F_A/R is defined as a following formula2.

F_AR=(H/2)/(F/2)=H/F   Formula 2

In other words, the aspect ratio at half maximum F_A/R is an aspectratio for a full width at half maximum (i.e., half height) F of the wall419.

In case that the aspect ratio at half maximum F_A/R is below 0.4, theheight H of the wall 419 is very low, thus an incident light from thelight emitting element ED does not travel to the substrate 401 but istrapped in the light emitting element ED, and thus a light extractionefficiency is reduced.

In case that the aspect ratio at half maximum F_A/R is over 0.8, theheight H of the wall 419 is very high, thus an incident light from thelight emitting element ED does not travel to the substrate 401 but istrapped in the wall 419, and thus a light extraction efficiency isreduced.

Particularly, in case that the aspect ratio at half maximum F_A/R isover 0.8, there is a tendency for a current efficiency enhancement ofthe light emitting element ED to be reduced, and in case that the aspectratio at half maximum F_A/R is in a range of 0.4 to 0.8, a currentefficiency enhancement of the light emitting element ED becomes amaximum value.

Thus, it is preferable that the aspect ratio at half maximum F_A/R ofthe wall 419 is set in a range of 0.4 to 0.8 in order to maximize alight extraction efficiency of the pixel region SP.

An aspect ratio at half maximum F_A/R over an aspect ratio A/R, Rm ofthe wall 419 is defined as a following formula 3.

Rm=(F_A/R)/(A/R)=D/2F   Formula 3

In other words, an aspect ratio at half maximum F_A/R over an aspectratio A/R, Rm is the aspect ratio at half maximum F_A/R divided by theaspect ratio A/R.

In case that the Rm is below 0.7, the height H of the wall 419 is verylow, thus an incident light from the light emitting element ED does nottravel to the substrate 401 but is trapped in the light emitting elementED, and thus a light extraction efficiency is reduced.

In case that the Rm is over 1.0, the height H of the wall 419 is veryhigh, thus an incident light from the light emitting element ED does nottravel to the substrate 401 but is trapped in the wall 419, and thus alight extraction efficiency is reduced.

Further, in case that the Rm is over 1.0, there is a tendency for acurrent efficiency enhancement of the light emitting element ED to bereduced, and in case that the Rm is in a range of 0.7 to 1.0, a currentefficiency enhancement of the light emitting element ED becomes amaximum value.

Thus, it is preferable that the Rm of the wall 419 is set in a range of0.7 to 1.0 in order to maximize a light extraction efficiency of thepixel region SP.

Referring to FIG. 13, it is seen that when the Rm is in a range of 0.7to 1.0 and the F_A/R is in a range of 0.4 to 0.8, a brightnessefficiency for a white is very high.

A slope S may mean a slope of a maximum angle between a tangent line tothe base surface portion 419 a and a horizontal plane.

Since a case of the slope S below 40 degrees is not very different in alight traveling angle from a case of no wall 419 being formed, the caseof the slope S below 40 degrees almost has no efficiency improvement. Ina case of the slope S over 80 degrees, a light traveling angle may begreater than a total reflection angle between the substrate 401 and anair outside the substrate 401, and thus an amount of a light trapped inthe light emitting element ED may greatly increase.

Thus, it is preferably that the slope S of the wall is set in a range of40 to 80 degrees in order to maximize a light extraction efficiency ofthe pixel region SP.

In this aspect, according to forming the gap G between the adjacentwalls 419, by setting the aspect ratio A/R of the wall 419 in a range of0.5 to 1.0, the aspect ratio at half maximum F_AR of the wall 419 in arange of 0.4 to 0.8, the aspect ratio at half maximum over the aspectratio, Rm of the wall 419 in a range of 0.7 to 1.0, and the slope S ofthe wall in a range of 40 to 80 degrees, an optimum condition tomaximize a light extraction efficiency is obtained.

In this regard, the gap G may be in a rage of 0.3 um to 10 um.

Further, the full width at half maximum F may be set in a range 1 um to2.5 um. In case that the full width at half maximum F is below 1 um orover 2.5 um, a light extraction efficiency by the wall 419 may bereduced.

In other words, in case that the full width at half maximum F of thewall 419 is below 1 um, an amount of a light, from the light emittingelement ED, reflected by the wall 419 and then extracted to thesubstrate 401 is less than an amount of a light diffuse reflected at thewall 419, thus an amount of a light trapped in the light emittingelement ED increases and thus a light extraction efficiency may bereduced.

Particularly, a light, which has an incidence angle less than a criticalangle of a total reflection, out of a light emitted from the lightemitting element ED may be extracted to the outside of the substrate 401through a multiple reflection between the side surface portions 419 c ofthe wall 419. In case that the full width at half maximum F of the wall419 exceeds 2.5 um, an amount of a light reflected between the sidesurface portions 419 c is reduced and thus an amount of a light outputto the outside of the substrate 401 is reduced.

In this aspect, the second insulating layer 416 formed with the firstand second layers 416-1 and 416-2 on the wavelength conversion layer 414is explained by way of example. Alternatively, a barrier layer mayreplace the first layer 416-1 to be formed on the wavelength conversionlayer 414, similarly to the aspect of FIGS. 7 to 9.

The barrier layer serves as an etch stopper on the wavelength conversionlayer 414 when forming the uneven layer 420, thus the wavelengthconversion layer 414 being exposed directly to the furrow 418 isprevented, and thus a problem by an exposure of the wavelengthconversion layer 414 is fundamentally prevented.

The barrier layer may have a thickness that corresponds to the shortestdistance L1 between the bottom surface 418 a of the furrows 418 and thewavelength conversion layer 414. In other words, the barrier layer maybe formed at the thickness of 0.1 um to 3 um to prevent the wavelengthconversion layer 414 being exposed to the furrow 418 when forming theuneven layer 420.

The barrier layer may be formed of a material not removed by adeveloping material (or an etching material) that is used in apatterning process of the second insulating layer 416.

Alternatively, the barrier layer may be formed of an inorganic material,for example, silicon oxide or silicon nitride. In other words, thebarrier layer may be formed of the same material as the first insulatinglayer 412.

According to the above-described aspects of the present disclosure, byemploying the uneven layer, an extraction efficiency of a light emittedfrom the light emitting element can be improved.

Further, the uneven layer can be formed without an exposure of thewavelength conversion layer overlapping the uneven layer, and thusreduction of reliability and lifetime of the wavelength conversion layerdue to the exposure of the wavelength conversion layer can be prevented.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in a display device of thepresent disclosure without departing from the sprit or scope of thedisclosure. Thus, it is intended that the present disclosure covers themodifications and variations of this disclosure provided they comewithin the scope of the appended claims and their equivalents.

What is claimed is:
 1. A light emitting display device comprising: alight emitting element including a light emitting layer disposed betweena first electrode and a second electrode; a wavelength conversion layeroverlapping the light emitting element; and an uneven layer including aplurality of furrows and a wall surrounding each of the plurality offurrows, the plurality of furrows and the wall disposed between thelight emitting element and the wavelength conversion layer, wherein abase surface portion of the wall is separate at a distance from thewavelength conversion layer.
 2. The light emitting display device ofclaim 1, wherein a shortest distance between the base surface portion ofthe wall and the wavelength conversion layer is in a range of 0.1 um to3 um.
 3. The light emitting display device of claim 1, furthercomprising: a circuit region including a thin film transistor connectedto the first electrode; a first insulating layer that covers the circuitregion and supports the wavelength conversion layer; and a secondinsulating layer that covers the first insulating layer and thewavelength conversion layer, wherein the uneven layer is formed at thesecond insulating layer overlapping the wavelength conversion layer. 4.The light emitting display device of claim 3, wherein the secondinsulating layer between the base surface portion of the wall and thewavelength conversion layer has a thickness in a range of 0.1 um to 3um.
 5. The light emitting display device of claim 1, further comprising:a circuit region including a thin film transistor connected to the firstelectrode; a first insulating layer that covers the circuit region andsupports the wavelength conversion layer; a barrier layer covering thewavelength conversion layer; and a second insulating layer covering thebarrier layer, wherein the uneven layer is formed at the secondinsulating layer overlapping the wavelength conversion layer, andwherein the barrier layer has a thickness corresponding to a separatedistance between the base surface portion of the wall and the wavelengthconversion layer.
 6. The light emitting display device of claim 5,wherein the barrier layer has a thickness in a range of 0.1 um to 3 um.7. The light emitting display device of claim 5, wherein the barrierlayer is formed of a same material as the first insulating layer.
 8. Thelight emitting display device of claim 1, wherein the wall includes: atop portion separate at a predetermined height from the base surfaceportion; and a side surface portion between the base surface portion andthe top portion.
 9. The light emitting display device of claim 8,wherein a cross-sectional area of the wall parallel to the wavelengthconversion layer increases as the cross-sectional area is close to thewavelength conversion layer.
 10. The light emitting display device ofclaim 8, wherein the side surface portion has a curved shape with aninflection point.
 11. The light emitting display device of claim 10,wherein each of the first electrode, the light emitting layer and thesecond electrode has a shape matching a contour of the uneven layer. 12.The light emitting display device of claim 11, wherein the side surfaceportion includes: an inflection portion including the inflection point;a first curved portion between the inflection portion and the basesurface portion; and a second curved portion between the inflectionportion and the top portion, wherein a thickness of the light emittingelement covering the inflection portion is less than that of the lightemitting element covering each of the first and second curved portions.13. The light emitting display device of claim 12, wherein the wall hasa height including a height ratio of the first curved portion, theinflection portion and the second curved portion to be 1:3:1.
 14. Thelight emitting display device of claim 12, wherein the wall has anaspect ratio in a range of 0.4 to 0.7.
 15. The light emitting displaydevice of claim 12, wherein base surface portions of neighboring wallsare separate from each other.
 16. The light emitting display device ofclaim 15, wherein the base surface portions of the neighboring walls areseparate at 0.3 um to 10 um, and wherein an aspect ratio of the wall isin a range of 0.5 to 1.0
 17. The light emitting display device of claim16, wherein the wall has an aspect ratio at half maximum in a range of0.4 to 0.8.
 18. The light emitting display device of claim 17, whereinthe aspect ratio at half maximum of the wall over the aspect ratio is ina range of 0.7to 1.0.
 19. The light emitting display device of claim 17,wherein a slope of an angle between a tangent line to the base surfaceportion and a horizontal plane is in a range of 40 to 80 degrees.